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Why are lead and cadmium separated from zinc by fractional distillation?
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zinc processing
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In the context of zinc processing, fractional distillation is used to refine zinc by exploiting the differences in boiling points between zinc and its common impurities.
The process is carried out in two stages using fractionating columns:
- Removal of Lead: In the first column, zinc is vaporized, leaving behind impurities with higher boiling points, such as lead and iron.
- Removal of Cadmium: The distilled zinc vapor is then condensed and transferred to a second column, where cadmium—which has a lower boiling point than zinc—is distilled off.
This two-step distillation refining process allows for the production of high-purity zinc by systematically separating elements based on their thermal properties.1